Interlaced scan is the original method of television and video acquisition. Until liquid crystal displays and plasma televisions became standard in the 2000's, all television displays (i.e., cathode ray tubes) were interlaced. At the current time, all standard definition television is interlaced. “True HD” (i.e., high definition) programming is still formatted as 1920×1080 interlaced at 60 hertz. Progressive scan is an alternative acquisition format (i.e., 1280×720 progressive or 1920×1080 progressive). After editing, video production is commonly a mix of interlaced and progressive material.
The transitions from one format to another can be anything from an abrupt switch (i.e., an advertisement splice) to a gradual dissolve where an interlaced scene is cross-faded onto a progressive scene. Additionally, video can comprise sections of interlaced video and progressive video composited spatially, for example, a progressive movie with an interlaced text “crawl” along the bottom.
It would be desirable to implement high efficiency video coding for video with interlaced and progressive content using lookahead.